Oxidation of silicon in an oxygen plasma generated by a multipolar electron cyclotron resonance source

Abstract

Silicon dioxide films with breakdown field strength ≳12 MV/cm and fixed charge density ∼3×1010 cm−2 were grown using an oxygen plasma generated by an electron cyclotron resonance source at 16 °C. This oxidation temperature is much lower than previously reported plasma oxidation of silicon, while the breakdown field and fixed charge density for these oxides are comparable to thermally grown oxide at high temperature. The oxidation rate was studied as a function of microwave power, pressure, rf power, source to sample distance, and oxidation time. The oxidation rate increases with microwave power but decreases with source distance and rf power. At pressure <5 mTorr, the oxidation rate increases rapidly with decreasing pressure. The oxide thickness increases with the oxidation time but the oxidation rate decreases. These oxide films were found to have oxygen to silicon ratio of 2 using x-ray photoelectron spectroscopy. From the ellipsometry measurements, these films show a refractive index around 1.47. These results indicate that high quality oxide films with properties that are similar to that of thermal oxide can be grown at low temperature.